I've not used purigen but have used PhosBan I think, if it's the Al based phosphate remover. Sadly it had one of it's not common, but not rare side effects of killing a bunch of softies (in my case star polyps, and sinularia) so I think it's better to use an iron based P remover like Rowaphos or similar. These are also a ton more effective. I don't fluidise, I mix it in with my carbon - I guess it's not super effective but it's ok for me